Conventionally, thermosetting furan resin compositions with the main component furan resin has furfuryl alcohol and furfural as raw materials, and since the cured product has excellent in heat resistance, solvent resistance and chemical resistance, it is used in various industrial fields as a matrix resin for laminates and composites such as steel pipe linings, joint cement, FRP, and the like.
Nevertheless, there is a problem in that there is substantial dimensional change in conventional thermosetting furan resin compositions due to dispersal of the water content derived from the condensation reaction during synthesis of the furan resin, and of the generated water derived from the curing reaction.
Based thereupon, a method proposed for reducing the water content (See Patent Document 1) is the removal by distillation of the water from the furan resin condensation when the synthesis is complete.
However, in this method, the viscosity of the furan resin increases exponentially with decreasing water content, and it is difficult to ensure the impregnation essential for the laminated body matrix resin.
On the other hand, after removal by distillation of the water from the condensation after the synthesis is completed, dilution with furfuryl alcohol or furfural is considered to be a method that reduces the viscosity while preventing dimensional change.
Nevertheless, it is necessary in this method to add large amounts of the volatile monomers of furfural and furfuryl alcohol, and deterioration of the working environment due to dispersal of the monomer becomes a significant problem.
Furthermore, preventing dimensional change due to dispersal of the generated water from the curing reaction in these methods was difficult.